A number of different arrangements of slackless type drawbar assemblies have been utilized by the railroad industry for several years, prior to the development of the present invention, as a means of connecting the adjacently disposed ends of a pair of freight cars together in a substantially semipermanent fashion. As is quite well recognized in the relevant freight car coupling art, each of these prior art type slackless drawbar assemblies have been equipped with a one piece drawbar member portion as one of the critical component parts thereof.
Such one piece drawbar member portion, of all these prior art type drawbar assemblies, is rotatably secured at each end thereof within the longitudinal opening of the center sill portion of each of such pair of freight cars closely adjacent a respective end thereof. This is the arrangement, even though each of the several different manufacturers and/or suppliers of slackless type drawbar assemblies to the railroad industry will supply them with their own particular design.
In the railroad industry, it is equally very well recognized that there will be at least as many as five such railway freight cars connected together using these slackless type drawbar assembly arrangements. Consequently, if it is assumed for the purposes of illustration only that there are five such freight cars which have been interconnected in this manner, if only a single end of only a single one of the four such slackless type drawbar assemblies required is in need of either repair or maintenance, then all five of the freight cars must be removed from any revenue generating type service while either such repair or maintenance is being performed.
In actual experience gained over the past few years, it has been conclusively demonstrated to the railroad industry that these slackless drawbar assembly arrangements will, as a general rule, require relatively frequent maintenance. One of the primary reasons why they require a significant amount of costly maintenance is because the design of these prior art type slackless drawbar assemblies requires that a relatively large number of component parts be used.
In addition, a number of these component parts will at least include some surfaces which are disposed in frictional engagement and which, also, must possess the capability of moving with respect to one another during in-track service. Such surfaces which are frictionally engaged will at least include one concave shaped surface and one convex shaped surface as well as a number of flat surfaces.
Furthermore, it is generally well recognized in the railway freight car coupling art that during such in-track service, each of these frictionally engaged surfaces will periodically be subjected to relatively large forces being exerted on them. Furthermore, at the same time, some relative movement will normally be occurring between such frictionally engaged surfaces. In the most extreme circumstances, the forces such frictionally engaged surfaces may be subjected to can be expected to exceed at least about one million pounds.
As would be expected, by those persons who are skilled in the mechanical art, the relative movement between these frictionally engaged surfaces will generate a significant amount of heat energy, particularly when they are being subjected to such extreme loads, which will significantly reduce the useful life span of these components.
Nevertheless, these slackless type drawbar assemblies, which are known to be in use at the present time, have generally provided the railroad industry with a much more modern style freight car coupling arrangement. For example, these slackless drawbar assemblies have substantially eliminated the need for a relatively expensive draft gear assembly as well as other freight car coupling components that were normally required before their introduction.
Furthermore, these slackless drawbar assemblies have generally resulted in an overall net decrease in the empty weight of such freight cars. This overall net weight reduction of such freight car is an extremely important factor to be taken into consideration by the user of such railway freight car in view of the ever rising energy cost.
It is believed to be equally well recognized, in the railroad industry, that these slackless drawbar assemblies are primarily installed on selected freight cars which will be utilized in a dedicated service type of application. The reason for this is that most of the freight cars that are utilized in this dedicated type service will not, as a general rule, require that they be uncoupled except for any routine maintenance and/or possible repair being required.
By way of example only, such freight cars which generally are used in such dedicated type service will at least include: coal cars, automobile and light truck transport cars and certain tank cars.
These slackless type drawbar assemblies have, nevertheless, gained a rather widespread acceptance in the railroad industry over the past several years in spite of the number of disadvantages which were discussed in some detail above. This would be expected, however, because there are a number of significant advantages that were gained by such railroad industry, in comparison to the older style standard type coupling arrangements which were and still are being used. Experience has demonstrated that these advantages far outweigh the disadvantages and such slackless drawbar assemblies have proven to the railroad industry over an extended period of time to be quite cost effective.